Add room upgrades

Fixes #155

lib/controllers/capabilities.dart

@@ -0,0 +1,14 @@
+import "package:flutter_riverpod/flutter_riverpod.dart";
+import "package:nexus/controllers/client.dart";
+import "package:nexus/models/capabilities.dart";
+
+class CapabilitiesController extends AsyncNotifier<Capabilities> {
+  @override
+  Future<Capabilities> build() =>
+      ref.read(ClientController.provider.notifier).getCapabilities();
+
+  static final provider =
+      AsyncNotifierProvider<CapabilitiesController, Capabilities>(
+        CapabilitiesController.new,
+      );
+}